FCStacks influence on number of wavefronts in-flight

" FCStacks - The number of flow control stack size used by the kernel (only for GPU device). This number may affect the number of wavefronts in-flight. To reduce the stack size, reduce the amount of flow control nesting in the kernel. " Could someone give some numbers, please. How this number will affect the number of simultaneously executed wavefronts on SIMD ? For example one of my kernels has FCStacks ==2, another one FCStacks ==6. In what case this number will be limiting factor?

EDIT: the kernel with FCStacks ==6 has pretty high GPR usage too, 55 GPRs used. What will limit number of wavefronts in this case? GPR usage or FCStacks value? And how many wavefronts per SIMD I could expect ?

Hi ryta1203,Thanks for correcting. Indeed in some cases less GPR usage and FCStack value might degrade the performance. Therefore the best way is:1. Go through the OpenCL Programming Guide before trying optimization.2. Do performance checks of your code using ATI Stream Profiler and SKA to identify the best optimization strategy in your case depending on the bottlenecks in performance.